Hyperthermia therapy (i.e., warming cancerous lesions utilizing the fact that cancer cells are more heat sensitive than normal cells) has been well known. The known methods of warming the lesions includes using electromagnetic waves. In using electromagnetic waves, the heat generated upon absorption of the electromagnetic waves applied to a living body is utilized for warming the living body, and there have been many reports in recent years of the effects thereof against malignant tumors.
Referring to FIGS. 1 and 2 an example of thermotherapy using high frequency warming will be explained. A region 3 of a living body 1 including a lesion 2 to be warmed as the target is put between two opposing plate-electrodes 4 and 5. High frequency current is caused to flow from a high frequency power source 6 across the plate electrodes 4 and 5 placed on the front and rear sides of the living body 1.
The degree of absorption of the electromagnetic waves is different depending on the tissues of the living body. For example, in the case of ultra high frequency waves, the absorption mainly occurs in the skin and muscle layers. On the other hand, high frequency waves are mostly absorbed in the fatty layer. Accordingly, when thermotherapy is carried out by warming the targeted lesion in the living body to a desired temperature by the pair of the electrodes disposed outside of the body, localized heating occurs near the surface of the living body to worry the patient with the undesired sense of heat and even cause a risk of burn at the surface layer tissue.
In order to avoid the feeling of heat and the risk of a burn to the surface layer tissue, it is necessary to cool the localized excessively heated portion. Accordingly, an electrode device of a structure provided with cooling means on the side of the plate electrode in contact with the living body as shown in FIG. 3 and FIG. 4 has been employed so far.
In FIG. 3 and FIG. 4, an electrode 7 made of a circular copper plate is connected by way of a lead wire 8 to a high frequency source (not shown). On the side A of the electrode 7 in contact with a living body, a spiral silicone rubber tube 9 is secured. A polymeric bag 10 in a rectangular configuration encloses the electrode 7 and the tube 9. Cooling water 11 is sealed within the polymeric bag 10 with an aim of cooling the localized excessively heated portion of the living body. The temperature of the cooling water 11 in the bag 10 is controlled by cooling water 12 circulating through the silicone rubber tube 9.
However, the conventional electrode device having the foregoing constitution involves various drawbacks upon actual use such as described below:
(1) Since the electrode device lacks in flexibility, it can not be in an intimate contact with the living body. Particularly, when it is applied to the surface of a living body with a small radius of curvature, an air gap is formed between the living body and the surface of the bag 10, which disturbs the distribution of the electric field. PA1 (2) Since the cooling with the cooling water 12 is performed indirectly by means of the cooling water 11, the cooling efficiency is poor. PA1 (3) Since there is no partitioning structure in the bag 10 for containing the cooling water, water flow may be deviated in the bag, causing uneven cooling.